A program of research into chemistry and biochemistry of dinoflagellate neurotoxins is proposed. Within this framework specific objectives include the isolation and characterization of the toxins of Gonyaulax tamarensis, the organism responsible for the red tides along the Atlantic costs of Canada and the U.S. The organism is known to produce several as yet uncharacterized toxins. Toxins will be isolated from organisms grown in laboratory culture as well as from scallops which typically exhibit a high toxin content when collected from areas of red tide infestations. It is further proposed to investigate the chemistry of saxitoxin with the aim of preparing structural analogs and radiolabelled derivation that might serve as specific probes and agents for the localization, isolation, purification, and structural characterization of the sodium channel in nerve membranes. Other objectives include the isolation and characterization of the toxins from other dinoflagellates, the development of rapid and quantitative toxin assay procedures, the elucidation of the biosynthesis of saxitoxin, and of environmental and biochemical parameters effecting toxin production, and the search for effective antidotes against these poisons.